Algal Bloom update: expect more dead fish and foam
Dead fish and foam are expected to continue to plague SA coastlines with changing weather conditions – but latest data shows some positive news.
At the weekly algal bloom update this morning, South Australian Research and Development Institute (SARDI) executive director Professor Mike Steer said despite a “significant reduction” in Karenia cell counts and plant material in local waters, he expected foaming events and dead leatherjackets would continue to wash up on the coastline.
Steer said high levels of plant material in the water was contributing to the “significant foaming events” seen across the state’s shores.
“We will continue to see foaming events in the future when we do have a change in (weather) conditions,” Steer said.
Latest South Australian Algal Bloom Water Testing and Monitoring Program testing results showed 18 of 21 onshore metropolitan sites showed zero or low levels of Karenia.
Three metropolitan sites recorded elevated levels including at Henley Beach Jetty with 240,000 cells of Karenia per litre, Grange Jetty at 110,000 cells per litre and West Beach Boat Ramp at 12,000 cells.
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Steer said this was a decrease in cell count from mid-October levels where six metropolitan sites recorded levels at over a million cells per litre.
SARDI would continue to conduct regular water sampling around the Southern Fleurieu and Kangaroo Island due to elevated Karenia counts in those areas, he said.
Two sites on the Fleurieu Peninsula recorded elevated levels of Karenia, with Parsons Beach recording 210,000 cells per litre and Waitpinga Beach 801,000 cells per litre, while 11,660 cells were recorded at American River on Kangaroo Island.
The elevated numbers in those areas were “expected” due to the circulation of currents around Gulf St Vincent.
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Steer said dead fish washing up on shores was “largely dominated” by species of leatherjackets.
“These fish form large, significant spawning aggregations, particularly around the bottom of the ocean and offshore,” Steer said.
“You’re going to get thousands of them as opposed to a single flathead or an isolated fish that swims through.”
He said the mix of Karenia species in the water compromised respiration in gill breathing organisms.
“These leatherjackets that are encountering those Karenia densities, particularly offshore in deeper water which we are monitoring, are succumbing to suffocation and floating to the surface and washing onshore with the onshore winds,” Steer said.
“We’re seeing larger episodes of a thicker foam that’s flying across our pavements because there’s a high amount of plant material already in the water.”
Environment Minister Lucy Hood said the “windy weather in November” was a contributor to the foaming events seen at Henley Beach and other metropolitan sites this week.
“We do continue to see a trending down of chlorophyll-a in the water, so that’s both harmful algae, other algae and various other plant material which is positive,” she said.
There also had been declines in brevetoxin concentrations in shellfish production areas but Steer had no update on the transportation of oysters as part of proposed shellfish restoration projects.
